Low-cement Refractory Concretes Research Articles

Low-Cement Refractory Concretes of Aluminum Silicate Composition Based on Submicron Aluminum Oxide Grade NK-Alumina 14

Low-Cement Refractory Concretes of Aluminum Silicate Composition Based on Submicron Aluminum Oxide Grade NK-Alumina 14

Cement-Free Refractory Concretes. Part 5. Cement-Free Refractory Concretes Based on Hydraulic Alumina Binders

CFRC based on alumina hydraulic binders are similar with respect to hardening mechanism to low-cement refractory concretes (LCRC) and ultralow cement concretes (ULCRC). They are characterized by significant strengthening in the heat treatment temperature range 200 – 300°C and severe weakening in the range 600 – 1000°C. By introducing silica sols or microsilica into their composition it is possible not only to reduce or eliminate the weakening effect, but also to increase their strength after firing due to mullite formation. CFRC based on alumina binders have improved thermomechanical properties compared with LCRC. Comparative evaluation of CFRC based on hydraulic binders with other types of refractory concretes is provided.

High-alumina cembor cements for low-cement refractory concretes

The Borovichi Refractories Combine developed and continues to make and use high-alumina (calcium- aluminate) cements Cembor-73 and Cembor-70 to produce refractory concretes and concrete products. This article discusses the main issues attending the production, composition, and properties of high-alumina cements of the Cembor series. These cements are compared to other Russian-made cements and similar cements made abroad. Recommendations on the use of cements Cembor-3 and Cembor-70 are made based on data on their composition and properties.

Bottom block for glass furnaces: fired or concrete?

Comparative studies of the properties of calcined fireclay articles and articles made of low-cement refractory concretes (LCRC), fired at different temperatures and non-fired, used for the masonry of the bottom structure of tank glass furnaces (bottom block) have been performed. Experimentally obtained data on the thermophysical properties, CLTE, glass stability of articles made of LCRC and calcined fireclay articles are presented. It is shown that fired fireclay articles are desirable to increase the service life of the furnace.

The thermodynamic basis for using aluminum-magnesium spinel in low-cement refractory concretes

The paper discusses the use of aluminum-magnesium spinel (previously synthesized or formed during use) in refractory concretes not only from the viewpoint of its high stability and scope for the formation of solid solutions with components of steel-melting slag and also of good thermophysical properties but also from the purposive reactive formation of structures with elevated high-temperature strength.

Advanced refractory articles and materials for the metallurgical industry

Data on some novel kinds of refractory articles and materials developed and produced by the Berezhnoy Ukrainian Research Institute for Refractories (Berezhnoy UkrNIIO) are presented. Corundum articles with Sialon binder and unshaped materials of various kinds (ramming mixtures, dry mixtures, traditional and low-cement refractory concretes) containing normal electrocorundum or refractory scrap instead of the costly white electrocorundum are described.

Ceramic castables: Concluding stage in the evolution of low-cement refractory concretes (part I)

Ceramic castables: Concluding stage in the evolution of low-cement refractory concretes (part I)

New-generation refractory concretes. Thermal processes, structure and high-temperature properties

Regularities of the processes of drying and heat treatment (firing) of new refractory concretes (ceramic concretes, low-cement refractory concretes, etc.) are considered. The conditions for the appearance of the effect of their explosive cracking (destruction) in drying are analyzed. Changes in the porous structure and some characteristics of the concretes (porosity, strength, shrinkage, expansion) are considered as functions of the temperature of their preliminary treatment. Regularities in the formation of the zonal structure and the stress state in use of refractory concretes are described. Data on the thermal conductivity and thermal expansion of refractory concretes of the Al2O3-SiO2 system are presented for a wide temperature range.

New-generation refractory concretes. Interrelation between structure formation and strengthening

A thermodynamic approach is used to consider the general regularities of structure formation in binding systems used in the technologies of new refractory concretes. The fundamental distinction in both the mechanism of structure formation and the kinetics of strengthening among different types of binding systems is determined by their colloidal-chemical activity. The main regularities of structure formation and strengthening of systems without chemical reactions are considered for clays and highly concentrated binder suspensions, and these regularities for systems with chemical reactions are considered for the binder system of low-cement refractory concretes. The importance of microsilica additions in concrete technologies is shown.

Refractory concretes of a new generation. Rheological aspect of their technology

The distinctive features of the rheological behavior of bonding systems and concrete mixtures are generalized and analyzed as applied to the technology of ceramoconcretes, low-cement refractory concretes, and liquid vibrocompacted thixotropic refractory mixtures. The foundations of the principle of rheotechnological correspondence in the technology of refractory concretes are formulated. An important role of vibrations for controlling the rheological properties (vibrorheology) is demonstrated. The principal factors decisive for the rheological properties of binders and concrete mixtures are analyzed. The important role of the temperature factor is considered and the problem of development of a “warm” technology of refractory concretes is posed. The processes of mixing in the technology of refractory concretes are also discussed.

A new generation of refractory concretes colloid-chemical aspect of their technology

Some peculiarities of the technology of new refractory concretes (ceramoconcretes, low-cement refractory concretes, and vibrocompacted thixotropic fluid refractory pastes) are analyzed from the standpoint of modern colloid chemistry. Interactions of disperse particles and the aggregation stability of disperse systems are discussed. Using a highly concentrated binding suspension (HCBS) of quartz glass as an example, a diagram of the regions of stability and coagulation of particles depending on the pH index of the suspension has been constructed. The state and form of the bonds of water in disperse systems are analyzed. It is shown for clays and HCBS of a number of materials that the strength properties of binders depend on the electrokinetic potential of the initial disperse system. A correlation between the acid — basic properties of the solid phase and the characteristics of the binder is demonstrated. The effects of heterocoagulation in systems with a mixed solid phase are also discussed.

New population of refractory concretes: Grain size composition and volume factors

We compared and analyzed “ideal” and actual curves for grain distribution in ceramic concretes and low-cement refractory concretes. Using a siliceous concrete as an example we studied the influence of the method of incorporating the highly dispersed component — the bond (in the form of VKVS or dry milled powder) — on its properties.